Add lexical scope and redefining variables in functions (#3015)

* Fix to allow variable shadowing inside functions

* Implement closures

* Fix KCL test code to not reference future tag definition

* Remove tag declarator from function parameters

This is an example where the scoping change revealed a subtle issue
with TagDeclarators.  You cannot bind a new tag using a function
parameter.

The issue is that evaluating a TagDeclarator like $foo binds an
identifier to its corresponding TagIdentifier, but returns the
TagDeclarator.  If you have a TagDeclarator passed in as a parameter
to a function, you can never get its corresponding TagIdentifier.

This seems like a case where TagDeclarator evaluation needs to be
revisited, especially now that we have scoped tags.

* Fix to query return, functions, and tag declarator AST nodes correctly

src/machines/modelingMachine.ts

@@ -1139,8 +1139,8 @@ export const modelingMachine = createMachine(
         )
         if (err(varDecNode)) return
         const sketchVar = varDecNode.node.declarations[0].id.name
-        const sketchGroup = kclManager.programMemory.root[sketchVar]
-        if (sketchGroup.type !== 'SketchGroup') return
+        const sketchGroup = kclManager.programMemory.get(sketchVar)
+        if (sketchGroup?.type !== 'SketchGroup') return
         const idArtifact = engineCommandManager.artifactMap[sketchGroup.id]
         if (idArtifact.commandType !== 'start_path') return
         const extrusionArtifactId = (idArtifact as any)?.extrusions?.[0]